PHP (Hypertext Preprocessor) is an open-source server-side scripting language built for the web. It runs on the server, generates HTML, and integrates natively with MySQL, PostgreSQL, Redis, and every major hosting provider. Over 75% of websites with a known server-side language still use PHP — including WordPress, Wikipedia, and Facebook’s early stack.

What is PHP?

PHP scripts execute on the server before the response reaches the browser. The web server (Apache, Nginx, or PHP’s built-in server) passes requests to the PHP interpreter, which runs your code and returns HTML, JSON, or other output.

Key characteristics:

  • Embedded in HTML — switch between markup and logic with <?php ... ?>
  • Loosely typed — variables do not require explicit type declarations (strict types available since PHP 7)
  • Request-oriented — each HTTP request bootstraps a fresh execution context
  • Mature ecosystem — Composer for packages, Laravel and Symfony for applications

History and Evolution

Year Milestone
1994 Rasmus Lerdorf creates Personal Home Page Tools
1997 PHP/FI 2.0 — form handling, guestbook
1998 PHP 3.0 — rewritten engine, wide adoption
2000 PHP 4.0 — Zend Engine, sessions, output buffering
2004 PHP 5.0 — OOP, exceptions, PDO for databases
2015 PHP 7.0 — 2× performance, scalar type hints, ?? operator
2020 PHP 8.0 — JIT compiler, named arguments, union types, attributes
2023 PHP 8.2+ — readonly classes, enums, improved performance

PHP 8.x is the only supported line for new projects. PHP 7 reached end of life in 2022.

How PHP Fits in a Web Request 

  Browser  →  Nginx/Apache  →  PHP-FPM  →  Your Script  →  Database
                ↓                              ↓
           Static files                    HTML / JSON response

A minimal PHP page:

  <?php
declare(strict_types=1);

$name = $_GET['name'] ?? 'World';
?>
<!DOCTYPE html>
<html>
<head><title>Greeting</title></head>
<body>
    <h1><?= htmlspecialchars($name, ENT_QUOTES, 'UTF-8') ?></h1>
</body>
</html>

Run locally:

  php -S localhost:8000
# Visit http://localhost:8000/?name=Simon

Modern PHP Example 

  <?php
declare(strict_types=1);

enum Status: string {
    case Active = 'active';
    case Inactive = 'inactive';
}

final class User
{
    public function __construct(
        public readonly int $id,
        public string $name,
        public Status $status,
    ) {}
}

function findActiveUsers(array $users): array
{
    return array_filter(
        $users,
        fn(User $u) => $u->status === Status::Active
    );
}

$users = [
    new User(1, 'Alice', Status::Active),
    new User(2, 'Bob', Status::Inactive),
];

foreach (findActiveUsers($users) as $user) {
    echo $user->name . PHP_EOL;
}
// Alice

PHP vs Other Languages

PHP vs Python

Both are beginner-friendly. PHP was designed specifically for web requests and ships with session handling, cookie support, and superglobals ($_GET, $_POST). Python is a general-purpose language; web development uses Django, Flask, or FastAPI. Choose PHP when deploying to shared hosting or maintaining WordPress/Laravel codebases.

PHP vs JavaScript (Node.js)

JavaScript runs in browsers natively and on servers via Node.js. PHP runs only on the server but has decades of web-specific tooling (Apache modules, PHP-FPM, hosting panels). Many teams use PHP for server-rendered pages and JavaScript for interactive front ends.

PHP vs Java

Java targets large enterprise systems with strict typing and long-running JVM processes. PHP bootstraps per request — simpler deployment on shared hosting, lower memory per idle connection. Laravel and Symfony bring enterprise patterns (DI, ORM, queues) to PHP.

Major Frameworks and Tools

Tool Purpose
Composer Dependency manager (like npm for PHP)
Laravel Full-stack MVC framework with Eloquent ORM
Symfony Component-based framework for enterprise apps
PHPUnit Unit and integration testing
PHPStan / Psalm Static analysis for type safety

Common Use Cases

  • Content management — WordPress, Drupal, Joomla
  • E-commerce — Magento, WooCommerce, custom Laravel shops
  • REST APIs — Laravel, Slim, Symfony API Platform
  • Legacy modernization — gradual PHP 8 upgrades with typed properties and enums

Security Essentials

PHP’s superglobals contain untrusted user input. Always:

  • Escape output: htmlspecialchars() for HTML, prepared statements for SQL
  • Validate input on the server, not just in JavaScript
  • Use declare(strict_types=1) and type hints in new code
  • Keep PHP and extensions updated

Getting Started

  1. Install PHP 8.2+ and Composer — see Installing PHP
  2. Choose an editor — see PHP IDEs
  3. Write your first script — Basic PHP Syntax

What Comes Next

This track covers syntax, forms, sessions, databases, OOP, Composer, Laravel, Symfony, security, performance, and deployment. PHP remains one of the fastest paths from zero to a deployed web application — and modern PHP is a far cry from the language’s early reputation.